The propagation of a pressure wave through an imploding liquid metal liner near turnaround, due to the compression of magnetic flux and plasma is considered, based on which the pressure distribution near turnaround is derived analytically under the assump-tion of a small Mach number M (defined by the ratio between characteristic radial velocity of liner and the velocity of sound through the medium). It is shown that under certain conditions, the rarefaction wave from the outer (free) surface causes the apparition of a negative pressure in the imploding liner, with consequent liability of cavitation. The crite-rion for the generation of the negative pressure is found to be MΛ>0.60.7 for the range of parameters considered (Λ : liner thickness at turnaround normalized by the inner radius).

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Noise analysis based on the autoregressive (AR) modeling technique has been applied to analyze the signals from fuel center thermocouples and cladding elongation detectors in-stalled in the instrumented fuel rods. The purpose of the present study is to extract ad-ditional information by means of the noise analysis, which could be of aid to deepen our understanding of in-reactor fuel rod behavior.
In order to investigate in detail the dynamic characteristics of the signals, a mode characteristic function (MCF) has been introduced. Evaluation of the MCF for the cladding elongation response to reactor power change indicated that the present technique has the potential to identify the point of contact between pellets governing the fuel stack elonga-tion. The power spectral densities (PSDs) for the cladding elongation and the fuel center tempsrature have been analyzed by means of spectral decomposition technique, which sug-gested the capability of extracting a certain information on the state of pellet-cladding interaction (PCI).
The present study indicates that the noise analysis technique applied here can provide useful information on the mechanical state inside fuel rods under irradiation.

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The NO removal by electron beam irradiation was studied in the moist NO-SO₂-O₂-N₂ mixtures containing NH₃. The NO removal was promoted markedly by addition of NH₃ and at the same time, SO₂ was removed. The formations of NO₂, N₂O, NH, NO₃ and (NH₄)₂SO₄ were observed in the mixtures containing NH₃. The NO removal increased with H₂O and SO₂ concentrations and was hardly affected by the presence of 319.5% O₂. The degree of the NO_x(NO+NO₂) removal became larger with decreasing temperature in the range of 80150°C. The NO removal was independent of dose rate in the range of 3.1X10⁴2.4X10⁶ rad/s. The promotion of the NO removal by addition of NH₃ is attributable to the effective decomposition of NO by NH₂ radical formed by the reaction of NH₃ with OH radical. The NO₂ yield decreased by addition of NH₃ and the N₂O yield increased.

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A separative power of a separating element, whose heads and tails separation factors are a and g, is expressed by ψ_b (a, β)=[α(β-1)In α-(α-1)In β]/(αβ-1) for the unit flow of the desired material and ψ_a(α, β)(≡ψ_b(β, α)) for that of undesired material. The additive properties of the functions ψ_b and ψ_a, were demonstrated by calculations of various types of ideal cascades, but the origin of the property is not obvious. The present study has furnished the mathematical basis of the additivity based on the special functional equa-tion. First, for symmetric processes (α=β), the functional equation which describes the function representing the quality of separation f(α, α) concerning the desired material was obtained and solved to give the functional form of f(α, α). The result was extented to the function f(α, β) representing the quality of asymmetric separation (α≠β). The derived function f(α, β) was demonstrated to be equal to ψ_b(α, β), and it was verified that functions ψ_b(α, β) and ψ_a(α, β) have the additive property in themselves.

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Radiodine in the reactor coolant is one of the indicators of failed fuel in the reactor. An improved method for radioiodine determination is required in order to reduce the analysis time and the radiation exposure for the radiochemist of a power station. For this reason, a new, rapid determination method with ion exchange paper was developed in the laboratory and examined at a power station for practical use.
The important features of the proposal are as follows :
(1) Recovery of radioiodine in the PWR reactor coolant including boric acid was 98%.
(2) The half-lives of radioiodines derived from the decay curve were nearly agreed with the reported values.
(3) Accuracy of this method was approximately equal to that of the conventional pre- cipitation method.
(4) This method reduced the analysis time to 1/61/9 of that of the conventional method.
(5) It took only 2 h to obtain the result after sampling, because interference of ¹³⁵Xe and ¹³⁵Xe, daughter nuclides of ¹³⁵I, could be eliminated.

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Both transverse and longitudinal Zircaloy-2 specimens irradiated up to 1.2 X 10²⁰ n/cm² (E>1 MeV) were tested in tension with strain rates ranging 1.1 X 10^-41.1 X 10^-2s^-1 in the temperature range 200400°C. Detailed observations of the specimen wall surface and microstructure were also made on samples deformed to various amounts of plastic strain, with a projector and an optical microscope.
It was found that localized plastic deformation bands occurred in the temperature range approximately 280330°C during straining to the ultimate tensile stress. Results also showed that the strain rate dependence of tensile properties, particularly the strain to the ultimate tensile stress, was associated with changes in the number and width of the localized deformation band with strain rates at a temperature of 300°C at which localized bands occurred. From a break of the straight line tracing the true stress-true plastic strain relationship, it was established that the onset stress and strain of the localized deformation band could be estimated.
The effect of specimen orientation on localized deformation band was also discussed on the basis of differences in the onset stress and strain between the transverse and longitu-dinal specimens.

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For sea disposal of the low-level radioactive wastes, high hydrostatic pressure tests on the full size (200l) multi-stage type packages were carried out in a pressure vessel. Using the data obtained, ingress of water through leak path was simulated by a computer analysis.
In order to confirm the above results, a demonstration test on integrity of the package in deepsea (5, 000 m depth) was carried out at 90 miles off Nojimazaki, Chiba-ken (143°10'E, 33°50'N) by hanging the package down to 5, 000 m depth. In these tests, no appreciable damage of the packages was observed which could give rise to controversy in safety.

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